Driver circuit and method for a semiconductor laser

Abstract

A driver circuit may comprise: a power control converts input power to an output voltage; a high frequency switch provides short duration pulses of output voltage causing a pulsed load current to flow through a load; a current sensor generates a signal representative of the pulsed load current; a sample and hold circuit samples the signal representative of the pulsed load current in synchronism with the high frequency switch and holds the sampled signal value; and a controller responds to the sampled signal value and applies control signals to the power control to produce the desired output voltage and to the high frequency switch and the sample and hold circuit to control the pulsed load current to a predetermined value. A corresponding method and an efficiency improver are disclosed. The load may include: a semiconductor laser diode (e.g., a green or blue semiconductor laser diode), or a light emitting diode.

What is claimed is: 
     
         1 . A driver circuit for supplying pulses of electrical power to a load comprising:
 a power control receiving input power and converting that input power to an output voltage;   a high frequency switch configured to provide short duration pulses of the output voltage to a load causing a pulsed load current of like duration to flow therethrough;   a current sensor through which the pulsed load current flows for generating a signal representative of the pulsed load current;   a sample and hold circuit configured to sample the signal representative of the pulsed load current in synchronism with the high frequency switch and to hold the sampled signal value; and   a controller receiving the sampled signal value and responsive thereto and to a reference value, and configured to apply control signals to the power control to produce the desired output voltage, and to the high frequency switch and the sample and hold circuit to control the pulsed load current to a predetermined value.   
     
     
         2 . The driver circuit of  claim 1  wherein the repetition rate of the pulsed load current is at least 55 KHz and the short duration thereof is less than 9 microseconds. 
     
     
         3 . The driver circuit of  claim 1  wherein the load includes:
 a semiconductor laser diode; or 
 a green semiconductor laser diode; or 
 a blue semiconductor laser diode; or 
 a light emitting diode. 
 
     
     
         4 . The driver circuit of  claim 1  wherein the controller:
 compares a measured value of the pulsed load current to a target value thereof, and 
 increases the output voltage and/or the duration of the pulsed load current pulses when the measured value of the pulsed load current is less than the target value thereof and decreases the output voltage and/or the duration of the pulsed load current pulses when the measured value of the pulsed load current is greater than the target value thereof. 
 
     
     
         5 . The driver circuit of  claim 4  wherein the controller:
 compares a measured value of the output of the load to a target value thereof, and 
 increases the duration of the pulsed load current pulses when the measured value of the output of the load is less than the target value thereof and decreases the duration of the pulsed load current pulses when the measured or computed value of the output of the load is greater than the target value thereof. 
 
     
     
         6 . The driver circuit of  claim 5  wherein the controller:
 determines a power consumption by computing power consumption of the load or computing power drawn from a power source; 
 stores the power consumption when the most recently determined value thereof is less than a previously stored value thereof; and 
 changes the duration of the pulsed load current pulses in a direction to further decrease the determined power consumption. 
 
     
     
         7 . A method for supplying pulses of electrical power to a load comprising:
 converting an input power to an output voltage;   providing high frequency short duration pulses of the output voltage to a load causing a pulsed load current of like duration to flow therethrough;   sensing the pulsed load current flow for generating a signal representative of the pulsed load current;   sampling the signal representative of the pulsed load current in synchronism with the high frequency short duration pulses and holding the sampled signal value; and   receiving the sampled signal value and a reference value, and applying control signals responsive to the sampled signal value and to the reference value to produce a desired output voltage and to control the high frequency short duration pulses and the sampling and holding to control the pulses of electrical power to a predetermined value.   
     
     
         8 . The method of  claim 7  wherein the high frequency repetition rate of the pulsed load current is at least 55 KHz and the short duration thereof is less than 9 microseconds. 
     
     
         9 . The method of  claim 7  further comprising:
 (a) establishing a target value as the reference value for the pulsed load current; 
 (b) measuring the value of the pulsed load current; 
 (c) comparing the measured value of the pulsed load current to the target value thereof, 
 (d) increasing the output voltage and/or the duration of the pulsed load current pulses when the measured value of the pulsed load current is less than the target value thereof and decreasing the output voltage and/or the duration of the pulsed load current pulses when the measured value of the pulsed load current is greater than the target value thereof; and 
 (e) repeating steps (b) through (d) of this claim. 
 
     
     
         10 . The method of  claim 9  further comprising:
 (a) establishing a target value for an output of the load; 
 (b) measuring the value of the output of the load; 
 (c) comparing the measured value of the output of the load to the target value thereof, 
 (d) increasing the duration of the pulsed load current pulses when the measured value of the output of the load is less than the target value thereof and decreasing the duration of the pulsed load current pulses when the measured or computed value of the output of the load is greater than the target value thereof; and 
 (e) repeating steps (b) through (d) of this claim. 
 
     
     
         11 . The method of  claim 10  further comprising:
 determining a power consumption by computing power consumption of the load or computing power drawn from a power source; 
 storing the power consumption when the most recently determined value thereof is less than a previously stored value thereof; and 
 changing the duration of the pulsed load current pulses in a direction to further decrease the determined power consumption. 
 
     
     
         12 . The method of  claim 7  wherein the load includes:
 a semiconductor laser diode; or 
 a green semiconductor laser diode; or 
 a blue semiconductor laser diode; or 
 a light emitting diode. 
 
     
     
         13 . A driver circuit for supplying pulses of electrical power to a light producing semiconductor device comprising:
 a power control including a DC converter receiving input power and converting that input power to an output voltage;   a high frequency switch transistor configured to provide short duration pulses of the output voltage to a light producing semiconductor device causing a pulsed light producing semiconductor device current of like duration to flow therethrough;   a current sensing resistor through which the pulsed light producing semiconductor device current flows for generating a signal representative of the pulsed light producing semiconductor device current;   a sample and hold circuit including a switch transistor configured to sample the signal representative of the pulsed light producing semiconductor device current in synchronism with the high frequency switch transistor and to hold the sampled signal value; and   a controller receiving the sampled signal value and responsive thereto and to a reference value, configured to apply a control signal to the power control to produce the desired output voltage, and to apply a pulse width modulated drive signal to the high frequency switch transistor and to the sample and hold circuit switch transistor to control the pulsed light producing semiconductor device current to a predetermined value.   
     
     
         14 . The driver circuit of  claim 13  wherein the repetition rate of the pulsed current in the light producing semiconductor device is at least 55 KHz and the short duration thereof is less than 9 microseconds. 
     
     
         15 . The driver circuit of  claim 13  wherein the light producing semiconductor device includes:
 a semiconductor laser diode; or 
 a green semiconductor laser diode; or 
 a blue semiconductor laser diode; or 
 a light emitting diode. 
 
     
     
         16 . The driver circuit of  claim 13  wherein the controller:
 compares a measured value of the pulsed light producing semiconductor device current to a target value thereof, and 
 increases the output voltage and/or the duration of the pulsed light producing semiconductor device current pulses when the measured value of the pulsed light producing semiconductor device current is less than the target value thereof and decreases the output voltage and/or the duration of the pulsed light producing semiconductor device current pulses when the measured value of the pulsed light producing semiconductor device current is greater than the target value thereof. 
 
     
     
         17 . The driver circuit of  claim 16  wherein the controller:
 compares a measured value of the output of the light producing semiconductor device to a target value thereof, and 
 increases the duration of the pulsed light producing semiconductor device current pulses when the measured value of the output of the light producing semiconductor device is less than the target value thereof and decreases the duration of the pulsed light producing semiconductor device current pulses when the measured or computed value of the output of the light producing semiconductor device is greater than the target value thereof. 
 
     
     
         18 . The driver circuit of  claim 17  wherein the controller:
 determines a power consumption by computing power consumption of the light producing semiconductor device or computing power drawn from a power source; 
 stores the power consumption when the most recently determined value thereof is less than a previously stored value thereof; and 
 changes the duration of the pulsed light producing semiconductor device current pulses in a direction to further decrease the determined power consumption. 
 
     
     
         19 . A method for supplying pulses of electrical power to a laser diode comprising:
 converting an input power to an output voltage;   providing high frequency short duration pulses of the output voltage to a laser diode causing a pulsed laser diode current of like duration to flow therethrough;   sensing the pulsed laser diode current flow for generating a signal representative of the pulsed laser diode current;   sampling the signal representative of the pulsed laser diode current in synchronism with the high frequency short duration pulses and holding the sampled signal value; and   receiving the sampled signal value and a reference value, and applying control signals responsive to the sampled signal value and to the reference value to produce a desired output voltage and to control the high frequency short duration pulses and the sampling and holding to control the pulses of electrical power to a predetermined value.   
     
     
         20 . The method of  claim 19  wherein the high frequency repetition rate of the pulsed laser diode current is at least 55 KHz and the short duration thereof is less than 9 microseconds. 
     
     
         21 . The method of  claim 19  further comprising:
 (a) establishing a target value as the reference value for the pulsed laser diode current; 
 (b) measuring the value of the pulsed laser diode current; 
 (c) comparing the measured value of the pulsed laser diode current to the target value thereof, 
 (d) increasing the output voltage and/or the duration of the pulsed laser diode current pulses when the measured value of the pulsed laser diode current is less than the target value thereof and decreasing the output voltage and/or the duration of the pulsed laser diode current pulses when the measured value of the pulsed laser diode current is greater than the target value thereof; and 
 (e) repeating steps (b) through (d) of this claim. 
 
     
     
         22 . The method of  claim 21  further comprising:
 (a) establishing a target value for an output of the laser diode; 
 (b) measuring the value of the output of the laser diode; 
 (c) comparing the measured value of the output of the laser diode to the target value thereof, 
 (d) increasing the duration of the pulsed laser diode current pulses when the measured value of the output of the laser diode is less than the target value thereof and decreasing the duration of the pulsed laser diode current pulses when the measured or computed value of the output of the laser diode is greater than the target value thereof; and 
 (e) repeating steps (b) through (d) of this claim. 
 
     
     
         23 . The method of  claim 22  further comprising:
 determining a power consumption by computing power consumption of the laser diode or computing power drawn from a power source; 
 storing the power consumption when the most recently determined value thereof is less than a previously stored value thereof; and 
 changing the duration of the pulsed laser diode current pulses in a direction to further decrease the determined power consumption. 
 
     
     
         24 . The method of  claim 19  wherein the laser diode includes:
 a semiconductor laser diode; or 
 a green semiconductor laser diode; or 
 a blue semiconductor laser diode; or 
 a light emitting diode.